As someone who's been knitting for over half my life, I vote for Knit fast, die warm because I have never seen it anywhere. Almost all of the other slogans are already available on tshirts through cafepress. Granted, they don't have a skull on them, but a lot of those slogans are getting pretty tired. Fonts like the ones that GG used are a dime a dozen too, if you really want to go that route, but I'd personally prefer a simple, bold font rather than the gothic-y illumination styled GG one.
Word up. It would be something not available anywhere else (at least, not anywhere that I've seen, and I shop A LOT).